Dental material mixer

ABSTRACT

A mixer for dental material adapted to agitate such materials in a conventional mixing capsule supported between the outer ends of a pair of arms which are actuated to oscillate the capsule along a closed path by an electric motor which drives a diagonal bushing that causes oscillation of said arms.

Unite 1 States Patent Folkenroth et a1.

DENTAL MATERIAL MIXER Inventors: Richard P. Folkenroth; William G.

Mader, both of York, Pa.

Dentsply International Inc., York, Pa.

Filed: July 14, 1971 Appl. No.: 162,470

Assignee:

References Cited UNITED STATES PATENTS 10/1967 Platt 259/72 X 6/1942 Chott 259/72 X 111 3,749,371 [451 July 31,1973

3,222,037 12/1965 Thiel et a1 259/72 3,411,755 11/1968 Strauss et a1... 259/72 3,533,601 10/1970 Woodham.. 259/2 2,106,609 1/1938 Krauss 259/72 UX 2,936,141 5/1960 Rapata 248/358 R 3,361,947 1/1968 Schlebusch 259/72 X Primary Examiner-William 1. Price Assistant Examiner-Philip R. Coe AttorneyC. l-lercus Just 5 7 ABSTRACT 13 Claims, 9 Drawing Figures a I I l I 4 '98 Q a /o J00 I1 8 a 2 12 //4 2 1 M J 22 32 /6 /2o 32 4' /a PATENTEB JUL 3 1 I975 SHEET 1 0F 3 H an M E .4 mm a n. J

Arromvzy PATENIELJUL31 ms SHEEI 3 OF 3 INVENTORS WILL/HM G. MAMA BY 19/0/4120 7. Foumvaam flrrommy DENTAL MATERIAL MIXER CROSS-REFERENCE TO RELATED APPLICATION The instant application covers the mechanical nov elty of a dental material mixer of which the aesthetic BACKGROUND OF THE INVENTION In the practice of dentistry, it is essential that certain dental materials be mixed to thoroughly blend the same in order to prepare them for use in certain types of dental prosthesis. Typical examples of dental materials of this type are dental cements, cavity liners, non-metallic filling materials, and amalgams. The individual ingredients which are mixed to produce a compound dental material used insuch dental prosthesis are maintained in separate condition until such use is desired. Within certain periods of time after the various types of materials are mixed, they harden or set after application thereof to dental cavities and the like incident to effecting such prosthesis.

It is conventional practice to mix such ingredients for said dental materials of the aforementioned type within a small capsule into which measured quantities of the various ingredients are introduced. The capsules are then placed within certain well-known types of mixing devices which provide a rapid oscillatory movement of the capsule in order to thoroughly mix the dental ingredients and materials. Under some circumstances, it is conventional to introduce a small weighted member, known as a pestle, within the capsule in order to enhance the mixing of the materials.

Typical examples of the mixing devices commonly used heretofore and at present are illustrated in U.S. Pat. Nos. 2,286,599, dated June 16, 1942; 3,222,037, dated Dec. 7, I965; and 3,411,755, dated Nov. 19, 1968. A more recent and also more sophisticated type of dental amalgam-preparing apparatus comprises the subject matter of US. Pat. No. 3,533,60l, dated Oct. 13, I970. Said structure includes means for discharging measured quantities of desired ingredients from reservoirs which are included with the apparatus into an oscillating member having a mixing compartment in which the ingredients are blended into an amalgam.

One of the principal difficulties resulting from operation of mixing devices such as those illustrated in said patents is that very objectionable noise is produced by the vibration of the machine. The noise is somewhat in the nature of a penetrating-type hum due to the imbalance of the vibrating means which supports the capsules or equivalent mixing chambers. In addition, said prior devices occupy a substantial amount of space in a dental operatory.

SUMMARY OF THE INVENTION It is the principal object of the present invention to provide a dental material mixer which minimizes the vibration of the oscillatory means by which the materials are mixed when enclosed within a conventional capsule by insulating various essential parts of the mixer from each other in a manner which transmits a minimum amount of vibration to the base of the machine, and correspondingly, to any supporting surface upon which the machine is positioned in a dental operatory or otherwise, such minimizing of vibration similarly minimizing the resulting noise produced by the machine when operating.

It is another object of the invention to introduce a certain amount of equilibrium into the means in the apparatus which restrain the oscillating elements of the mixer to operation within predetermined limits and thereby minimize wear upon the driving mechanism for the oscillating members, as well as permit the motor to initiate operation under a balanced load rather than an unbalanced load as is customary in substantially all of currently used mixers of the type to which the present invention pertains. 4

It is a further object of the invention to eliminate all rigid connections between the oscillating elements of the mixer and the base and enclosing housing thereof through the employment of a plurality of vibrationabsorbing members in the various connections between certain elements and devices of the mixer, rubber grommets of suitable elastic property, without restriction thereto, being the preferred form of vibrationinsulating means employed in the mixer.

Details of the foregoing objects and of the invention, as well as other objects thereof, are set forth in the following specification and illustrated in the accompanying drawings comprising a part thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of a dental material mixer embodying the principles of the present invention, part of the casing broken away to illustrate certain details thereof.

FIG. 2 is a side elevation of the mixer shown in FIG. 1 as viewed from the right-hand side thereof, part of the casing being broken away to expose details of some of the operating mechanism with greater clarity.

FIG. 3 is a top plan view of the mixer shown in FIGS. 1 and 2 with part of the casing being broken away to expose details of the operating mechanism in the mixer.

FIG. 4 is a side elevation of the operating mechanism I of the mixer which is exposed in FIG. 3, part of the illustration in FIG. 4 being shown in section, and the housing being removed to simplify the view.

FIG..5 is an enlarged fragmentaryvertical elevation of part of the driving mechanism for the oscillatory portion of the mixer illustrated in the preceding figures.

FIG. 6 is a detailed plan view of part of the vibration damping means included in the operating mechanism as seen on the line 6--6 of FIG. 4.

FIG. 7 is a fragmentary diagrammatic view illustrating the path of movement described by the capsulesupporting portion of the oscillatory mechanism of the mixer which is produced by a diagonally extending bushing on the drive shaft of the motor which is illustrated in FIG. 5.

FIG. 8 is a vertical sectional elevation of one example of vibration-absorbing means employed between two elements of the mixer as viewed on the line 8-8 of FIG. 3, said elements being illustrated in phantom.

' FIG. 9 is a perspective diagrammatic view showing in full lines the various vibration-absorbing means and movement restraining elements employed in the mixer, the elements with which said vibration-absorbing and movement restraining means are associated being illustrated in phantom in order to simplify the view and otherwise to orient the relationship between said various means in a concise manner.

DETAILED DESCRIPTION Referring to FIGS. 1 and 2, it will be seen that the mixer comprising the present invention includes a casing or housing which may be made by molding or casting from any suitable material, such as metal, synthetic resin, or otherwise. The base 16 is provided with a sloping front panel 12 upon which suitable control knobs l4 and 15 are mounted. A preferably planar base 16 also is provided which may be made preferably from rigid material, such as sheet metal. Said base also preferably is provided with resilient feet or knobs 18, one example of which may comprise rubber buttons.

The supporting elements 18 are adapted to rest upon a suitable supporting surface 20, such as a counter in a dental operatory, the top of a suitable cabinet, or even the bottom of a drawer within which the mixer may be positioned and readily concealed when not in use. To adapt the same to storage within a drawer, for example, it will be seen, especially from FIGS. 1 and 2, that the vertical profile of the machine is relatively low and the mechanism enclosed therein has been suitably proportioned and arranged to make such low profile possible. The base 16 may be secured, for example, to the molded casing 10 by any simple, suitable means, such as relatively long screw 22 which is threaded into an appropriate boss 24 formed in the casing 10.

The operating mechanism of the mixer comprising the invention includes an electric motor 26 of suitable horsepower. Frame means 28 comprising a plurality of interrelated elements supports the motor 26 relative to the base 16. Said frame means 28 comprise a similar pair of vertical brackets 30 which may be formed from sheet metal, for example, and are provided with horizontal feet 32 which are suitably fixed to the base 16 by any appropriate means, such as rivets, screws, or otherwise.

The frame means also include a U-shaped member 34, which also may be formed from sheet metal. As best seen from FIG. 2, the member 34 is mounted with the horizontal bight portion 36 uppermost, whereby the legs of the member 34 depend downwardly therefrom. The member 34 is of limited width, as best seen from FIG. 3, and an extension plate 38 projects essentially horizontally in one direction from the under surface of the bight portion 36 of U-shaped frame member 34, the plate being affixed thereto by spot-welding, rivets or otherwise, not shown.

As indicated above, one of the principal objectives of the present invention is to minimize the transmission of vibration, in particular to the base 16 and supporting surface on which it rests from the motor 26 and certain driving mechanism connected thereto and actuated thereby, which is described in detail hereinafter. Minimum vibration also produces minimum noise resulting from operation of the mixer, and the latter especially is a further objective of the invention. To this end, it

-will be seen that the downwardly extending legs of the U-shaped bracket 34 are connected to the upstanding brackets 30 by vibration-absorbing means or units 40, details of which are best shown in FIG. 8.

It will be seen that said vibration-absorbing means in the specific illustration shown in FIG. 8 and certain of the other figures, preferably comprise a grommet 42, formed from rubber or rubber-like material, the periphery of which is provided with an angular groove which receives the perimeter defining a hole 44 formed in each of the depending side legs of the U-shaped frame member 34. The grommet 42 is formed with a central hole of suitable size to receive the shank of a connecting screw 46 which is threaded into complementary threads formed within the flanged tubular nuts 48, industrially known as Tee Nuts, the flanged head preferably being of a geometrical configuration, such as a hexagon, to permit the use of a wrench therewith.

The upper end portion of each of the brackets 30 also is provided with a suitable hole through which the shank of screw 46 extends. The head 50 of the screw engages the outer surface of bracket 30 and secures the same against one face of the grommet 42, while the head of the tubular nut 48 engages the opposite face of grommet 42 and thereby secures the legs of the U- shaped framed member 34 respectively to the brackets 30 in a manner which will minimize the transmission of vibration from the member 34 to the brackets and, correspondingly, to the base 16 and casing 10 of the mixer.

To further augment the vibration-absorbing effect afforded by the grommet 42, it will be noted especially from FIGS. 3 and 4 that the motor 26 has one end of its shaft 52 projecting outwardly beyond the bracket 30 and U-shaped frame member 34 for purposes of supporting and actuating capsule supporting and oscillating means 54. Considering the motor and said capsule supporting and oscillating means 54 as a unit, which they actually comprise, it can be observed from FIGS. 3 and 4 that the centers of the several vibrationabsorbing means 40 are substantially in line with the center of gravity of the combined motor 26 and capsule supporting and oscillating means 54, which is the theoretic no-motion location, thereby further contributing substantially to minimization of transmission of vibration from said combined mechanism to the base 16 and/or casing 10, as well as any supporting surface 20, upon which the mixer rests for support.

To further contribute to the insulation of vibration from said motor and capsule supporting and oscillating means to the base 16 and casing 10, attention is directed to FIGS. 3, 4 and 9, wherein it will be seen that the bight portion 36 of the member 34 and extension plate 38 support additional vibration-absorbing units 56, which, for simplicity, preferably are similar to the vibration-absorbing means 40, described hereinabove and also illustrated in said figures, as well as FIG. 8. Referring particularly to FIG. 4, it will be seen that the vvibration-absorbing units 56 comprise grommets 58 which are similar to the grommets 42. The angular grooves in the grommets 58 receive the perimeters which define holds 60 which are formed in extension plate 38.

Flanged, tubularnuts 62, similar to nuts 48, extend through central holes in grommets 58 to receive clamping bolts 64 which are threaded into suitable sockets formed in the upper end of the housing of motor 26, as is clearly evident from FIG. 4. Such arrangement very largely insulates from the frame means 28 vibrations which are generated by the motor 26 and the capsule supporting and oscillating means 54 which are directly connected thereto. Thus, it will be seen further that the vibration-absorbing units 56 supplement and cooperate with the vibration-absorbing means 40, described above, to minimize the transmission of vibrations directly to the base 16 of the mixer unit.

The shaft 52 supports and drives a relatively heavy hub 66 which is of such size that it functions to an efrotation, as well as against relative longitudinal, separative movement.

Referring to FIG. 5, it will be seen that hub 66 is centrally bored inward from its outer end to receive a bolt 72 by means of which an oscillation-producing bushing or driving member 74 is tightly clamped to the hub 66 for rotation therewith. The bushing 74 has a central bearing portion 75 which is cylindrical and the bushing is bored diagonally to the axis of said central portion so that the axis of the bore is at a very acute angle to the axis of said central bearing portion and bolt 72, as well as the axis of the motor 26.

The inner races of a pair of similar anti-friction bearings 76 are mounted upon the central portion 75 of bushing 74 and are suitably fitted so as to be rotatable therewith. The outer races of the bearings 76 are received within a complementary cylindrical opening 78 which is formed in oscillatory arm 80. The lower end of said arm is slotted at 82, as shown in FIG. 2, and a clamping bolt 84 extends through suitable holes in the projecting lower end portions of the slotted end of arm 80 in order to tighten said opening 78 of arm against the outer races of bearing 76.

The arm 80 also is provided at diametrically opposite sides of the intermediate portion thereof with pairs of similar ears 86, which are best shown in FIGS. 2 and 3. Pins or bolts 88 extend perpendicularly through said ears in parallel manner with respect to the axis'of opening 78 in the arm 80, for purposes to be described hereinafter.

Oscillatory movement of the arm 80 is restrained to operation within a predetermined limit by means of a bracket 90 which may be formed from wire or rod stock, for example. The shape of said bracket is best seen from FIGS. 2-4. The bracket is somewhat U- ered to be one of the novel and meritorious features of the present invention.

The oscillatory'arm 80 of the capsule supporting and oscillating means 54 supports a pair of arms or legs 104, one end of each of which are disposed within suitable shallow grooves, not shown, which are formed in opposite faces of the upper portion of the arm 80. The upper portions of the arms 104 are provided with oppositely extending recessed means 106 within \which the opposite ends of a mixing capsule 108 may be securely mounted for oscillatory movement of the capsule by the means 54. Firm lodging and retention of the opposite ends of capsule 108 within the recessed means 106 is assured by the provision of a plurality of relatively strong leaf springs 1 10, which bear against the mid portions of the outer sides of arms 104 and the overlying end portions of said springs and arms are effectively secured to the upper end of oscillatory arm 80 by means of bolts 112.

OPERATION The motor 26 is energized by means of current supplied through power conduit 114 which is connected to a starting switch that is operable by button 1 15, which is associated with control knob 15 that operates a timer unit 116, shown in FIG. 2. Suitable circuitry, not

shown, also connects an adjustable speed control unit 1 17 of commercial type in the circuit between the starting switch and the motor 26, said speed control unit being adjusted and actuated by knob 14. In view of the fact that circuitry of this type is of conventional nature,

shaped and has a bight portion 92 which is supported bracket 90 preferably form obtuse angles with the bight portion 92 of the bracket, so that it will be seen that the shape of the bracket is not exactly U-shaped, but only generally so. For purposesv of ready'd'esignation, how ever, bracket 90 is considered to be substantially U- shaped in this description, as well as the appended claims.

The arms 98 terminate in notch-forming ends 100 for purposes of loops on the outer endsof tension springs 102 being disposed within the bases of said notches, while the opposite ends of the springs have loops through which the pins or bolts 88 extend. It will be seen that such an arrangement produces an equilibrium condition with respect to the oscillatory arm 80 upon the central portion 75 of bushing 74, in such manner that the energizing of the motor may occur under a balanced load condition rather than an unbalanced load situation as is that in dental mixing devices presently used, examples of which are illustrated in said aforementioned patents. Such balanced feature is considdetailed description thereof is believed to be unnecessary.

When the motor 26 has been energized by means of the aforementioned button 115 of the starting switch and the time period of operation has been selected by disposing timer knob 15 where desired, the oscillatory unit 54 which supports the capsule 108 is oscillated at a speed detennined by the setting of the speed control unit 117 which is operated by knob '14. Different types of dental products require different optimum time periods and speeds of oscillation to effect the thorough mixing of the ingredients thereof. Certain cements, for example,.must be mixed quickly and used quickly before final setting occurs, whereas the mixing of metallic amalgams require longer periods of time and at different speeds from those required for mixing cements.

Referring to FIG. 7, a diagrammatic illustration is included in the form of a path outline 118, defined by successive arrows, which is generated by the oscillatory means 54 upon the capsule 108. It will be seen that the path is somewhat in the nature of a figure eight. If viewed axially of the motor 26, however, the path is somewhat arcuate, generally about the axis of bolt 72. Such a movement of the capsule has been found to effect highly desirable results in the mixing of substantially all types of dental material which require such mixing. The path or orbit within which the capsule 108 moves may be considered to be a nutation, and correspondingly, the oscillatory means 54 can be termed a nutation assembly.

In considering the nutational orbit or path of movement of the capsule 108, it can be appreciated that such movement, particularly at the upper end of an arm of reasonable length which is composed ofoscillatory arm and the pair of arms 104 which are secured thereto, very substantial vibration is imposed upon the motor 26, the shaft 52 of which comprises substantially the main support of the oscillatory means 54. In view of the purposely provided mass and weight of the hub 66, however, which is directly rotated by the motor shaft, a certain amount of gyroscopic effect is produced which tends to minimize vibration of the motor. Also, the cooperating pairs of vibration-absorbing means of units 40 and 56 additionally and substantially insulate the base 16 from receiving such vibrations imposed upon the motor 26. Further, the mounting of vibrationabsorbing units 40 opposite the center of gravity of the motor and oscillating means 54 thereon, as well as the provision of the equilibrium condition which the springs 102 and their supporting means tend to produce with respect to the support of the oscillatory arm 80 upon the motor shaft, also tend to minimize the vibration imparted to the motor, as distinguished from theresult of using only a single movement-restraining spring connected to the oscillatory arm and the lack of any vibration-absorbing means, as is conventional in dental mixing devices presently in use. i

A further means tending to insulate movement of the motor 26 and means 54 from being transmitted to the base 16 is provided in the form of a pin having a threaded nut thereon or a bolt 120 which is connected to the lower portion of the motor 26, near the rear end thereof, as best shown in FIG. 4. A rigid disc-like supporting member 122 is secured by rivets 124 or the like, see FIGS. 4 and 6, to the rim portion of a large hole formed in base 16. The supporting member 122 also is provided with a large hole within which a rubber grommet is mounted. The periphery of the grommet is grooved to receive the perimeter of said large hole formed in member 122 and the center of the grommet is provided with a perpendicularly extending hole which preferably contains athin-walled metal sleeve 128 through which the pin or bolt 120 extends. The material from which the rubber grommet 126 is formed is preferably quite pliable so as to minimize the transmission of vibratory movement of the motor to base 16.

The grommets 42 of vibration-absorbing units 40 and grommets 58 of vibration-absorbing units 56 preferably are formed from rubber compounds having a Shore A durometer number between approximately 50 and 75, the optimum number being approximately 70. The grommet 126 attached to member 122 also has similar characteristics. Said grommets may also all be formed from synthetic resins suitably formulatedto provide equivalent physical characteristics, within the spirit and purview of the present invention. a

Without restriction thereto, the mixing device comprising the present invention is capable of operating within a speed range, for example, of between approximately 2,500 and 7,000 r.p.m. Such a range affords a wide latitude which is highly useful to adapt the mixer to accommodating substantially all types of dental materials which require mixing through vibration within capsules and similar mechanisms.

From the foregoing, it will be seen that the present invention provides a dental mixer which is capable of a wide range of speeds which, in conventional mixers, tend to produce substantial and objectionable vibration which produces irritating and highly objectionable noise in a dental operatory. The noise is of a type which is very penetrating and actually is a loud irritating hum of substantial magnitudepBy minimizing the transmission of such noise between the elements of the mixer which produce the same and the base of the mixer which supports the mechanism, the resulting vibration which is imparted to the base and easing of the mixer is tremendously minimized and reduced over that which is found in conventional dental mixers.

Such minimizing of the vibration upon the base of the mixer and, correspondingly, upon any surface which supports the same, is effected by the utilization of appropriate vibration-absorbing means at critical locations, certain of which are adjacent the center of gravity of the motor and oscillatory unit operated thereby. The use of a heavy hub, in conjunction with the rotor of the motor, serves in the capacity of a flywheel and produces a certain amount of gyroscopic effect which also contributes to the desired results of reducing or minimizing vibration and noise. Still further, the equilibrium provided by using a pair of movementrestricting springs which are connected to opposite sides of the capsule supporting an oscillating means contributes to the desired effect, as well as increasing the life of the driving mechanism.

While the invention has been described and illustrated in its several preferred embodiments, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways falling within the scope of the invention as illustrated and described.

.We claim:

1. Apparatus for mixing ditferent'dental materials comprising in combination:

a. A base adapted to be disposed upon a supporting surface,

b. frame means comprising brackets connected to and extending upward from said base,

c. motor support means,

d. vibration absorbing means interconnected between said motor support means and said brackets to minimize transmission of vibrations therebetween,

e. a motor connected to said motor support means,

f. capsule supporting means,

g. drive means forsaid capsule supportingmeans connected thereto and] to said motor and operable to oscillate said capsule supporting means, and

h. movement limiting mechanism including'elastic means connected to said drive means and operable to restrain the oscillating movement of said capsule supporting means within predetermined limits.

2.". The mixing apparatus according to claim 1 in which said brackets are positioned adjacent opposite sides of said motor and said vibration-absorbing means between said brackets and motor support means being positioned substantially opposite the center of gravity of said motor and drive means connected thereto.

3. 'The mixing apparatus according to claim 1 in which said motor support means is a substantially U- shaped frame member having opposite legs which are connected to said brackets by said vibration-absorbing means.

4. The mixing apparatus according to claim 3 in which said U-shaped frame member is connected to said motor by additional vibration-absorbing means disposed between said frame member and motor.

5. The mixing apparatus according to claim 4 in which the bight portion of said U-shaped frame member is positioned above said legs in the operative position of said apparatus and said motor is connected to said frame member below said bight portion in depending manner.

6. The mixing apparatus according to claim further including a stabilizing member depending from said 5 motor and said apparatus further including movementabsorbing means mounted between said stabilizing member and said base to limit the vibration of said motor relative to said base when said apparatus is operating without appreciably transmitting such vibrations to said base.

7. The mixing apparatus according to claim 1 in which said motor has a shaft projecting from one end thereof,

i. bushing means fixed to said shaft having an axis at an acute angle to the axis of said shaft and extending rotatably through a bearing in one end of said capsule supporting means,

which the other end of said capsule supporting means comprises a pair of arms respectively engageable with opposite ends of a mixing capsule to support the same with the axis of said capsule disposed generally parallel to the axis of said motor.

9. The mixing apparatus according to claim 7 which further includes a bracket having a pair of arms supported by said motor support means and said arms extending toward said one end of said capsule oscillating means, the outer ends of said arms being spaced substantially equally at opposite sides of the axis of said motor, and said elastic means comprising tension springs, the outer ends of said arms respectively engaging one end of each of said springs and the opposite ends of said springs being connected to opposite sides of said one end of said capsule oscillating means.

10. The mixing apparatus according to claim 9 in which said one end of said capsule supporting means is provided with a pair of ears respectively projecting diametrically away from the axis of said motor and said opposite ends of said springs being connected respectively to said ears.

11. The mixing apparatus according to claim 9 in which said motor support means is substantially U- shaped and the bight portion thereof being supported by said brackets of said frame means and adapted to permit limited pivotal movement of the arms of said motor support means about an axis extending transversely between the arms of said motor support means.

12. The mixing apparatus according to claim 7 further including a hub of substantial 'mass and weight fixed to said motor shaft and rotatable therewith, said hub being adjacent said bushing means and providing a flywheel effect.

13. The mixing apparatus according to claim 12 in which said bushing is fixed directly to the outer end of said hub by a bolt which is coaxial with the shaft of the motor and hub and is threaded at the inner end thereof into said hub.

2 ORM PO-IOSO (10-69) UNITED STATES ,PA'IENT OFFICE CERTIFICATE OF CORRECTION 3,749,371 Dated July 31, 1973 Richard P. Folkenroth et al.

Patent No.

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 48, "vvibration should read H. vibration+ Claim 7, line 3, after "thereof," insert and further including: Claim 7, line 19, "supporting" should read H supported Signed and sealed this 8th day of January 1974 (SEAL) Attest:

RENE D. TEGTMEYER EDWARD M.FLETCHER,JR-.

Acting Commissioner of Patents Attesting Officer usqo -oc scan-Poo f U.S. GOVERNMENT FRI "Tl OFFICE I!!! O-Jii-JSI, 

1. Apparatus for mixing different dental materials comprising in combination: a. A base adapted to be disposed upon a supporting surface, b. frame means comprising brackets connected to and extending upward from said base, c. motor support means, d. vibration absorbing means interconnected between said motor support means and said brackets to minimize transmission of vibrations therebetween, e. a motor connected to said motor support means, f. capsule supporting means, g. drive means for said capsule supporting means connected thereto and to said motor and operable to oscillate said capsule supporting means, and h. movement limiting mechanism including elastic means connected to said drive means and operable to restrain the oscillating movement of said capsule supporting means within predetermined limits.
 2. The mixing apparatus according to claim 1 in which said brackets are positioned adjacent opposite sides of said motor and said vibration-absorbing means between said brackets and motor support means being positioned substantially opposite the center of gravity of said motor and drive means connected thereto.
 3. The mixing apparatus according to claim 1 in which said motor support means is a substantially U-shaped frame member having opposite legs which are connected to said brackets by said vibration-absorbing means.
 4. The mixing apparatus according to claim 3 in which said U-shaped frame member is connected to said motor by additional vibration-absorbing means disposed between said frame member and motor.
 5. The mixing apparatus according to claim 4 in which the bight portion of said U-shaped framE member is positioned above said legs in the operative position of said apparatus and said motor is connected to said frame member below said bight portion in depending manner.
 6. The mixing apparatus according to claim 5 further including a stabilizing member depending from said motor and said apparatus further including movement-absorbing means mounted between said stabilizing member and said base to limit the vibration of said motor relative to said base when said apparatus is operating without appreciably transmitting such vibrations to said base.
 7. The mixing apparatus according to claim 1 in which said motor has a shaft projecting from one end thereof, i. bushing means fixed to said shaft having an axis at an acute angle to the axis of said shaft and extending rotatably through a bearing in one end of said capsule supporting means, j. and a plurality of elastic means supporting in opposition to each other and engaging said one end of said capsule supporting means at opposite sides thereof, whereby a nutational path of movement of said other end of said capsule supporting means is effected when said motor is energized and said path of movement is elastically restrained within predetermined limits.
 8. The mixing apparatus according to claim 7 in which the other end of said capsule supporting means comprises a pair of arms respectively engageable with opposite ends of a mixing capsule to support the same with the axis of said capsule disposed generally parallel to the axis of said motor.
 9. The mixing apparatus according to claim 7 which further includes a bracket having a pair of arms supported by said motor support means and said arms extending toward said one end of said capsule oscillating means, the outer ends of said arms being spaced substantially equally at opposite sides of the axis of said motor, and said elastic means comprising tension springs, the outer ends of said arms respectively engaging one end of each of said springs and the opposite ends of said springs being connected to opposite sides of said one end of said capsule oscillating means.
 10. The mixing apparatus according to claim 9 in which said one end of said capsule supporting means is provided with a pair of ears respectively projecting diametrically away from the axis of said motor and said opposite ends of said springs being connected respectively to said ears.
 11. The mixing apparatus according to claim 9 in which said motor support means is substantially U-shaped and the bight portion thereof being supported by said brackets of said frame means and adapted to permit limited pivotal movement of the arms of said motor support means about an axis extending transversely between the arms of said motor support means.
 12. The mixing apparatus according to claim 7 further including a hub of substantial mass and weight fixed to said motor shaft and rotatable therewith, said hub being adjacent said bushing means and providing a flywheel effect.
 13. The mixing apparatus according to claim 12 in which said bushing is fixed directly to the outer end of said hub by a bolt which is coaxial with the shaft of the motor and hub and is threaded at the inner end thereof into said hub. 